With the rapidly expanding development of personal computers into the field of first what were termed portable, then lap-top, and now notebook size computers, there has been a tremendous demand for maintaining the performance of the disc drive systems of such computers. The major development in this direction has been the development of smaller Winchester-type disc drives as replacements and enhancements to floppy disc drives for program storage. The Winchester disc drive, in general, provides higher capacities and faster speeds of operation, factors which are of great importance for the effective use of personal computers running advanced software packages.
The Winchester-type disc drives that have been developed for the personal computer market were initially based on the use of hard discs of a diameter of approximately 5.25 inches. Many of these disc drives used stepper motors for positioning a transducer over a selected track on the rotating disc, although larger capacity systems typically used voice coil motors. The next step in reduction of size of the disc drive was to cut the "form factor" (the dimensions of the external case for the complete disc drive) by one half, so that the resulting disc drive used a platter of 3.5 inch diameter. The height of the disc drive was also becoming a significant factor, and efforts were made to reduce the height of the disc drive as well, so that the size of the casing for the personal computer could be minimized. However, as to most lap-top and notebook computers, hard disc drives continue to be external devices.